Target sleeve



F. c. SOUTH TARGET sLEEvE Sept. 19, 1961 FRA/VK SUTH BY MN Q E 04C ATrREYs F. C. SOUTH TARGET SLEEVE Sept. 19, 1961 Filed March 26, 1946 FIG. 4

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nited States Patent F 3,000,634 Y TARGET SLEEVE Frank C. South, Princeton, NJ., assignor to the United States of America as represented by the Secretary of the Navy e Y Filed Mar. 26, 1946, Ser. No. 657,185

3 Claims. (Cl. 273-1053) The present invention relates to aerial dummy targets of the type known as target sleeves. A sleeve per se is a prior-art device adapted tolbe towed by an airplane in order to give aerial gunners, fighter pilots and antiarcraft gun crews practice in shooting at a moving target.

In accordance with the invention there is provided an arrangement whereby a target sleeve is surrounded with an intense high-freqency energy eld for detonating missiles equipped with proximity fuzes, of the general character disclosed in the co-pending patent application of Wilbur S. Hinman and Harry Diamond, Serial No. 537,983, led in the United States Patent Oiiice on May 30, 1944, now Patent No. 2,812,113, and that of Merle A. Tuve and Richard B. Roberts, Serial No. 471,388, filed in the United States Patent Oce on January 6, 1943, now abandoned, both of which are assigned to the same assignee as the present invention and patent application. Some of the energy generated by a fuze of this type Ais reflected from a target such as an airplane or surface vessel. This energy causes the firing of the fuze totake place. It is therefore electrically desirable that the surface of the sleeve be large and highly reflective. However, the necessity of withstanding miscellaneous stresses imposed by acrobaties at great speeds requires that the sleeve be small with the result that it presentsv a relatively small reflecting surface. Moreover, it is structurally desirable that the sleeve be made of materials which are not ecient radiators of high-frequency energy. The desired structural characteristics of prior-art sleeves have made them ineflicient for proximity fuze testing for the reason that the sleeve reflections are relatively weak.

The invention solves the problem so presented by providing a separate source of high-frequency radiation, closely adjacent the target sleeve, to create an intense selfgenerated field of radiation similar in itsefrects on the fuze to the reflected eld that would surround a relatively much more extensive object, made of highly reflective material, such as an actual plane or ship.

While the invention may be embodied in many Vequivalent forms, only a few have been selected for illustration, and are shown in the accompanying drawings, wherein:

FIG. l is a diagrammatic elevational View of a signal generator in accordance with the present invention parts being shown in section;

FIG. 2 is a schematic showing of the electrical circuit arrangements for producing high-frequency signal-energy, the section being taken substantially on line 2-2 of FIG. l;

FIG. 3 shows the generator interposed between a target sleeve and a tow line;

FIG. 4 shows a modified form of signal-generator in accordance with my invention. f

FIG. 5 shows another modified form of signal-generator in accordance with the present invention.

FIG. 6 shows diagrammatically a modified circuit; for generating and radatinghigh frequency oscillations,

Referring lirst to FIG. 1, there is shown a streamlined casing 11 having a rotatable head 12 at its forward end. A shaft 13 extending through the casing and head, terminates in eyes 14 and 15, eye 14 being adapted to be secured to a tow line. Stabilizing fins 16-16 are so formed on the casing as to minimize spinning of the casing.

The head is so mounted as to be freely rotatable on shaft 13, and is formed with tins l17--17. These tins are Patented sept. 19, 1961 inclined, so that the head spinsV rapidly when the apparatus is towed through the 'air at high speed by an airplane.

AA pair of radially disposed metallic blades `1S are carried bythe head'and turn therewith concentrically about the axis of the shaft. Within the casing is a container 19, adapted to house batteries or other auxiliary devices (not shown). Another container 20 houses vacuum tubes and associated circuit elements connected therewith, presently to be described with particular reference to FIG. 2. A

The tank circuit of the signal generator comprises a generally circular section ofA resonant transmission line 21. The anodes (not shown) of triode vacuum tubes 22 and 23 are connected to the line terminals by conductors 24 and 25, while the grids `(not shown) are connected to the ends of an inner coaxial conductor 28 by leads 26 and 27.Y The inner conductor is insulated from the line. It should be noted that the grid and anode of each tube are connected to opposite ends of the inner and outer conductors, as shown by the cross-over in FIG. 2. e

The mid-point of wire 28 is grounded to container 20 by conductor 29 and resistor 30, while the mid-point of line 21 is connected to the positive terminal of a B-battery (not shown).

Antennas 31-31 are connected to line 21 at points symmetrically located with respect to its mid-point, condensers 32-32 being individually included in the coupling circuits. Insulators 33-33 are provided to pass the lead-in wires through casing 11.

When proper connectionsgare made to a conventional cathode heating-current source, oscillations are produced in-the tank. The line section is so arranged that its midpoint is at a node of potential while at the same time the high-frequency current is at its maximum at that point. The current gradually` decreases with distance from Vthis central point, while the voltage increases correspondingly. The antennas 31-31 are connected to the tank at points removed from the center. At points still further removed from the center of line 21 two flat plates 34--34 are electrically connected to the line and thus subjected to high frequency voltages of considerable intensity. These plates are nearly in the same plane as blades 18 so that the plates and blades constitute a variable condenser. As the blades rotate with head 12, this condenser runs through all its capacity values twice in each turn. As the condenser is shunted across a portion of the line its capacity variations cause corresponding variations in the frequency of the generated oscillations.

Thus when the casing 11 is interposed between a tow line 35 and a target sleeve 36, as shown in FIG. 3, the antennas 31-31 continually radiate high frequency signals, the frequency of which swings through a range determined by the variation of capacity of the condenser comprising the elements 18 and 34-34.

Passing now to FIG. 4, a slightly modified shape of casing 11 is shown, wherein are placed A and B batteries as indicated. The head 12' is substantially the same as head 12, and likewise has tins 17 thereon to cause it to rotate. The tins 1616 are shaped somewhat differently from those of FIG. 1, and it will be understood that many other specific forms maybe used.

In the FIG. 5 embodiment the casing 38 does not have a separate head. Instead, the rotation is produced'by a two-bladed wind-wheel 39 mounted on a tubular shaft V40, al thrust bearing 41 being provided near the plane-of the wind wheel. The main shaft 13 is continuous from eye `14 to eye 15 as in the other forms. The shaft 40 carries the rotor 42 of a direct current generator having a stator 43. These parts are indicated only diagrammatically and it will be understood that the elements 42 and 43 represent the armature and field of a direct current generator of the high voltage type that serves as a. substitute for a B battery.

As power is here drawn from the wind wheel 39, there will, of course, be a resulting torque tending to turn the casing 38 in the same direction as the wheel. This may be resisted effectively by giving the fins 44-44 a suitable twist to cause them to tend to turn in the opposite direction.

The casing 38 may be made of non-conducting material if desired and the antennas 45-45 are directly supported by the fins, so that these elements mutually reenforce one another without interfering with their proper functions.

The conductive blades of the wheel 39 here take the place of the blades 18 of FIGS. l and 4, and the stationary condenser plates 46-46 are located near the plane of the wind wheel, so that the movable blades or plates thereof will cause the capacity to vary during rotation. The circuit connections are as indicated in FIG. 6.

Here a circuit almost identical with that of FIG. 2 is disclosed. The tubular line 21 (here opened into horseshoe shape for ease of illustration) is connected at its ends to the anodes of tubes 22 and 23 by leads 24 and 25 while the grids are connected in reverse order by leads 26 and 27 to the ends of the inner conductor 28. The mid-point of conductor 28' is connected to ground through wire 29 and resistor 30 while the mid-point of line 21 is connected to the positive terminal of generator 42-43.

The antennas 45-45 are connected to line 21 at symmetrically located points on opposite sides of the potential node, condensers 32-32 being included in the coupling circuits. The plates 46-46 are preferably connected to line 21 near the ends thereof, where the high frequency voltage is greatest, so that the maximum effect of blades 39--39 is obtained.

The operation of the devices is as follows:

Referring rst to FIGS. 1, 2 and 3, the apparatus is arranged in the tow line of the target sleeve as shown in FIG. 3 and when aloft emits radiations from its signal generator. These radiations fluctuate in frequency due to the variations in capacity of the condenser, formed by the rotating blades 18 and the stationary plates 34-34. These fluctuations themselves occur at a recurrence rate determined by the rotation of the head 12, and within a frequency range determined by the capacity of that condenser. At the extremely high frequencies contemplated, of the order such that the length of line 21 is of one-half of the mean wave length, even very small capacities have great effects. The interelectrode capacities of the tubes and the distributed capacities of the line and associated conductors and condenser 18, 34-34 constitute substantially all the capacity present in the oscillator frequencydetermining circuit.

The net result is that radiations having a wide sweep of high frequencies are continuously sent out from the antennas. As all the magnitudes, electrical and mechanical, may be predetermined, it is possible to generate a field of radiation of known intensity, such that it will satisfactorily detonate a proximity fuze, of the type disclosed in the above-mentioned copending applications, approaching the apparatus.

As this field is usually large compared to the size of the sleeve, the fact that the source of oscillations is not centered in the sleeve becomes of minor importance, and errors from this cause are negligible.

The frequency sweep is suiciently broad to include all reasonable limits in the allowable frequency characteristics of individual fuzes and to ensure their detonation.

The operation of the FIG. 4 form is substantially the same as that of FIGS. 1 and 3. Although the antennas 4 are not shown in FIGURE 4, it will be understood that they may be provided in duplicate and arranged symmetrically, as in FIG. 1.

The chief difference between the FIG. 5 form and those described above, is that there the rotary head is modified into a wind-turbine having the blades 39, which turbine does two things: First, it supplies power to operate the direct current generator 42, 43 and to supply the B voltage, and second, its blades act as the movable plates of the bridging condenser, to swing the frequency.

From the above disclosure, it will be understood that the invention may be embodied in various forms, all of which accomplish the essentially same purposes. It will also be understood that while specific radio circuits are shown, the broad aspect of the invention is independent of such details.

Inasmuch as many forms besides those disclosed specically may readily be designed, the invention is defined solely by the following claims.

I claim:

1. The combination of an aerial target sleeve adapted to be employed in practice with ordnance missiles of the type including a proximity fuze, a radio frequency signal generator of the sweep-frequency type carried adjacent to said target sleeve for producing thereabout a radiant energy field, and means coupling said signal generator to said sleeve whereby a missile will be `detonated upon its approach to said target.

2. A device for use in aerial target practice with missiles of the type including a proximity fuze, comprising a casing adapted to be towed by an aircraft, means for retaining said casing adjacent the target, a wind-operated ,power means, a rotary condenser carried by said casing and actuated by said power means, and a radio frequency signal generator mounted with said casing having a frequency-determining circuit including said rotary condenser for producing about said target a radiant energy field, thereby to detonate a missile upon its approach to the target.

3. A device for use with a target sleeve for detonating missiles having proximity fuzes, said device comprising a casing of such shape as to present little resistance to movement through the air, means for retaining said casing adjacent said target sleeve, a power means mounted on said casing and driven by the movement of the device through the air, a radio frequency signal generator mounted within said casing, said signal generator including a resonant circuit having a variable capacitor, and means coupling said variable capacitor to said power means, whereby said power means governs the frequency of said generator by varying the capacitance in the resonant circuit thereof.

References Cited in the file of this patent UNITED STATES PATENTS 

